2 Adding a quote block to show difference between suggested wording & explanation
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on 'Date' I am planning to meet up with a long time friend from high school and we have some catching up to do. It will take the better part of the day, so you might want to look for some activities you can do on your own.

on 'Date' I am planning to meet up with a long time friend from high school and we have some catching up to do. It will take the better part of the day, so you might want to look for some activities you can do on your own.

This is nice enough, to the point and suggestive enough that she will understand she is not invited. Should she invite herself, tell her your other friend isn't good with other people and you rather have a more intimate get together between long time friends.

on 'Date' I am planning to meet up with a long time friend from high school and we have some catching up to do. It will take the better part of the day, so you might want to look for some activities you can do on your own.

This is nice enough, to the point and suggestive enough that she will understand she is not invited. Should she invite herself, tell her your other friend isn't good with other people and you rather have a more intimate get together between long time friends.

on 'Date' I am planning to meet up with a long time friend from high school and we have some catching up to do. It will take the better part of the day, so you might want to look for some activities you can do on your own.

This is nice enough, to the point and suggestive enough that she will understand she is not invited. Should she invite herself, tell her your other friend isn't good with other people and you rather have a more intimate get together between long time friends.

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source | link

on 'Date' I am planning to meet up with a long time friend from high school and we have some catching up to do. It will take the better part of the day, so you might want to look for some activities you can do on your own.

This is nice enough, to the point and suggestive enough that she will understand she is not invited. Should she invite herself, tell her your other friend isn't good with other people and you rather have a more intimate get together between long time friends.